Photonic switches are increasingly used to switch signals in optical networks. A photonic switch may be based on a Mach-Zehnder interferometer (MZI) with a carrier-effect based phase shifter in one or both arms of the MZI. A carrier-effect based phase shifter is typically based on a positive (p-type)-intrinsic (i-type)-negative (n-type) (i.e., PIN), or positive (p-type)-negative (n-type) (i.e., PN), electrical diode. These types of switch structures are known as push-only (PIN or PN diode in one arm) or push-pull (PIN or PN diode in both arms) configurations. An MZI with integrated carrier-effect based phase shifters can provide a compact and low power optical switch having sufficiently fast switching speed for use in metro networks and data center switching applications. Further, the carrier-based optical switches or “switching cells” can be successfully used to construct larger-scale switch fabrics, allowing on-chip integrated optical switch matrices of large size (e.g., 64×64) to be fabricated.
Carrier-effect based phase shifters are susceptible to a self-heating effect caused by electrical power (Joule heating) dissipated mainly in the intrinsic region of a PIN or in the junction region of a PN diode operating under steady-state condition. As a result, a self-heating effect takes place in one of the MZI arms. It increases the operational temperature at this arm and also creates a temperature gradient across the structure. This leads to an additional and unwanted phase shift induced in one arm of the MZI and, in turn, degrading the optical extinction ratio of the switch.
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